1. Field of the Invention
The present invention relates to a conductive landing pad of a semiconductor device which connects a lower plug with an upper interconnection, and more particularly, to a semiconductor device and a method for manufacturing the semiconductor device in which a contact area between a lower plug and a landing pad is increased, so that detachment of the landing pad from the lower plug or a wafer can be prevented.
2. Description of the Related Art
Semiconductor devices have a multi-layered structure, in which upper interconnections are connected to lower plugs by landing pads formed in the interlevel dielectric (ILD) film between the upper interconnection and the lower plug. In general, the landing pad is formed of tungsten having a low resistivity. Unfortunately, tungsten also has strong tensile strength, so it has poor adhesiveness with respect to the ILD film made of silicon oxide, in which the landing pad is located. As a result, the landing pad made of tungsten is liable to be detached from the ILD film or a wafer. This detachment problem is inevitable when the landing pad is formed of a material having poor adhesiveness to the ILD film.
In particular, an ILD film is deposited over lower plugs and etched to form grooves for landing pads. Following this, a conductive material, for example, tungsten, is deposited over the ILD film to fill the grooves, and subjected to mechanical and chemical polishing using a slurry until the ILD film is exposed, thereby resulting in completed landing pads. The slurry used in the mechanical and chemical polishing aggregates by heat generated as the wafer is turned, so that it cannot be easily removed from the wafer. When the mechanical and chemical polishing is continued, the surface of the wafer is scratched and the landing pad formed of tungsten is separated from the ILD film and the lower plugs.
When the formation of the landing pad is completed, the wafer with the landing pad is subjected to washing and drying processes. The drying process is performed by spin drying. xe2x80x9cSpin dryingxe2x80x9d refers to removing water used in the washing process from the wafer surface by centrifugal force generated as the water is turned. Although the landing pads remain in the ILD film through the mechanical and chemical polishing process, it is more likely that the landing pads passed through the mechanical and chemical polishing process are liable to be detached from the wafer surface during the spin drying processes. The separation of the landing pads causes poor electrical connections in the resultant semiconductor device. Furthermore, the detachment of the landing pads becomes serious with an increase in the integration density of semiconductor devices.
To account for the detachment of landing pads, a technique of placing an adhesive layer formed of TiN or TaN, which has excellent adhesiveness to an ILD film, between the ILD film and landing pads formed of tungsten has been suggested. Although the adhesive layer is interposed between the ILD film and the landing pads, the landing pads cannot remain intact in the ILD film through subsequent mechanical and chemical polishing, washing and drying processes, which are carried out after filling grooves for landing pads in the ILD. On the other hand, in order to ensure strong adhesiveness between the landing pads and the ILD film with the adhesive layer, the landing pads must be larger than a predetermined dimension, which restricts the integration density of semiconductor devices.
Another approach used to overcome the detachment of landing pads is to increase the contact area between landing pads and lower plugs by etching a lower insulating layer, in which the lower plugs are to be formed, as well as the ILD film to form grooves for the landing pads. However, this overetching technique needs a lower insulating layer having increased thickness to ensure a sufficient processing margin for deep grooves, so that the aspect ratio of openings for the lower plugs formed in the lower insulating layer increases. In this way, because the grooves for the landing pads are formed over the ILD film and the lower insulating layer, the aspect ratio of the grooves also increases. Such increased aspect ratios cause difficulties in etching the ILD film and the lower insulating layer. In addition, the openings for the lower plugs and the grooves for the landing pads are filled with conductive materials, voids more likely occur within the openings and the grooves. With the increase in the integration density of semiconductor devices, these problems become serious.
To solve the above problems, it is an objective of the present invention to provide a semiconductor device having a combination of lower plugs and a conductive layer, and a method for manufacturing the semiconductor device, in which separation of the conductive layer from an interlevel dielectric film (ILD) and the lower plugs can be suppressed even when a fine pattern is adopted to increase the integration density of semiconductor devices.
It is another objective of the present invention to provide a semiconductor device having a combination of lower plugs and a conductive layer, and a method for manufacturing the semiconductor device, in which less consideration is needed in etching openings for the lower plugs and grooves for the conductive layer, and prevents occurrence of voids in the lower plugs and the conductive layer.
According to an aspect of the present invention, there is provided a semiconductor device including a first interlevel dielectric (ILD) film having an opening. A diffusion barrier layer is formed along the first ILD film having the opening. A lower plug having a recession is formed in the opening coated with the diffusion barrier layer. The semiconductor device also includes a second ILD film having a groove through which at least the recession of the lower plug is exposed, the second ILD film being formed over the first ILD film. An adhesive layer is formed on the groove of the second ILD film and the recession of the lower plug. A conductive layer is deposited on the adhesive layer to fill the groove of the second ILD film and the recession of the lower plug.
The adhesive layer may be formed on a portion of the recession of the lower plug, or over the recession of the lower plug according to the processing conditions. It is preferable that the diameter of the recession is xc2xc-xc2xd of the diameter of the opening of the first ILD film.
The lower plug may be formed of a metal, preferably, aluminum, copper or tungsten. The conductive layer may be formed of a metal such as tungsten, copper, aluminum, refractory metal and refractory metal silicide.
According to another aspect of the present invention, there is provided a method for manufacturing a semiconductor device. In accordance with the method, a first interlevel dielectric (ILD) film is formed with an opening over a semiconductor substrate. A diffusion barrier layer is formed along the first ILD film having the opening. A first conductive layer having a recession is formed in the opening of the first ILD film coated with diffusion barrier layer, and a second ILD film having a groove, through which at least the recession of the lower plug is exposed, is formed over the first ILD film. A metal is deposited over the second ILD film having the groove to form an adhesive layer on the groove of the second ILD film and the recession of the lower plug. A conductive layer is formed over the adhesive layer such that the conductive layer fills the groove of the second ILD film and the recession of the lower plug. In the manufacture of the semiconductor device, the first conductive layer is a lower plug, and the second conductive layer is a landing pad.
In another embodiment, the semiconductor device manufacturing method according to the present invention comprises preparing a semiconductor substrate in which an active region is defined. A first interlevel dielectric (ILD) film with an opening, through which the active region is exposed, is formed over the semiconductor substrate. A diffusion barrier layer is formed along the first ILD film having the opening. A first conductive layer is deposited over semiconductor substrate having the diffusion barrier layer, such that the opening of the first ILD film is not completely filled. The first conductive layer and the diffusion barrier layer are etched until the surface of the first ILD film is exposed, thereby resulting in a lower plug having a recession. A second ILD film having a groove, through which at least the recession of the lower plug is exposed, is formed over the first ILD film. A metal is deposited over the second ILD film having the groove to form an adhesive layer on the groove of the second ILD film and the recession of the lower plug. A second conductive layer is formed over the adhesive layer such that the second conductive layer fills the groove of the second ILD film and the recession of the lower plug. The adhesive layer and the second ILD film are etched until the surface of the second ILD film is exposed, so that a landing pad filling the groove and the recession is formed.
The adhesive layer may be formed on a portion of the recession of the lower plug, or over the recession of the lower plug according to the processing conditions. It is preferable that the diameter of the recession is xc2xc-xc2xd of the diameter of the opening of the first ILD film.
In one embodiment, forming the lower plug includes forming a conductive material layer over the first ILD film having the opening coated with the diffusion barrier layer, such that the opening of the first ILD film is not completely filled. The conductive material layer is etched until the top of the first ILD film is exposed. The conductive material layer can be etched by mechanical and chemical polishing.
In one embodiment, forming the conductive layer includes forming a conductive material layer over the second ILD film coated with the adhesive layer such that the groove of the second ILD film and the recession of the lower plug are completely filled. The conductive material layer is etched until the top of the second ILD film is exposed. The conductive material layer can be etched by either mechanical and chemical polishing or dry etching.